Anatomy of the Male Genital Tube in Goleojptera. 607 



the different groups, and even in allied species. In the 

 Scarabaeidae it is nearly always excessively large, and is 

 often produced into long diverticula (i. e. Hexodon, fig. 25a). 

 In Lucanidae it is found in every stage, from a simple form, 

 in which it is scarcely distinguishable from the stenazygos, 

 to a form such as Lucanus cervus (fig. 8). In this species 

 the internal sac is not drawn into the median lobe, but 

 when at rest it is folded down on to the broad median 

 lobe. The sac is produced into a long flagellum, supported 

 on each side by a thin strip of chitin ; the stenazygos* 

 continues through the flagellum to its tip. To obtain a 

 similar position of the orifice in Cerambycidae the great 

 sac must be completely everted. 



The phenomenon of the internal sac being permanently 

 everted is not confined to the Lucanidae, but appears 

 among the Scarabeidae, Heteroceridae and Lycidae. In 

 Spilota regina (fig. 20) the armature of the sac consists of 

 two strong chitinous projections from the apex, and a strong 

 chitinous plate beset with stout spines, the basal part of 

 the sac being membranous. A comparison with allied 

 forms demonstrates that these structures are part of the 

 internal sac, and that the median lobe is normal in shape 

 and size. In Metriorrhyiiclius (fig. 186) there is no doubt 

 as to the everted condition of the internal sac, and it may 

 be doubted whether its invagination is possible in some of 

 these cases. 



The flagellum appears in various conditions, as to size, 

 etc., in different families or portions of families. In the 

 Brenthidae it reaches an enormous length and fineness, 

 and at the base the stenazygos can be seen running into 

 the flagellum, but further on they appear to amalgamate, 

 as we cannot separate them. Among the Staphylinidae 

 PinopMlus rectus has an enormous flagellum coiled up 

 within the median lobe. The other forms of armature 

 situated on the internal sac are very various, and have 

 been described in many species in the special anatomical 

 part of this memoir; cf. various species of Dmiacia (fig. 

 199), and Carpophagus (fig. 204a). 



In another portion of this memoir we show that in many 



* In the special anatomical portion of this memoir we have 

 always spoken of this stenazygotic portion of the tube as the "ejacu- 

 latory duct," but this is a functional term, and by other writers is 

 often applied to the internal sac; it would probably be well to 

 abandon it. 



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